Non-contact test solution for antenna-on-package (aop) devices using near-field coupled rf loopback paths

ABSTRACT

A radio frequency (RF) loopback substrate or printed circuit board (PCB) which contains receive and transmit antennas located on the bottom of the loopback substrate which are aligned with the complementary transmit and receive antennas on an antenna on package (AOP) device under test. The loopback substrate receive and transmit antennas are coupled to each other. The device under test contacts are driven by a conventional tester, which causes RF circuitry in the integrated circuit to drive an AOP transmit antenna. The corresponding loopback substrate receive antenna receives the RF signal from the AOP transmit antenna and provides it to the loopback substrate transmit antennas. The integrated circuit package AOP receive antennas then receive the RF signals from the loopback substrate transmit antennas. The signals at the integrated circuit package AOP receive antennas are monitored through the integrated circuit contacts to monitor the received RF signals.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/381,921 filed Apr. 11, 2019, which claims the benefit under 35 U.S.C.§ 119(e) of U.S. Provisional Patent Application Ser. No. 62/781,496entitled “Non-Contact Test Solution for Antenna-On-Package (AOP) DevicesUsing Near-Field Coupled RF Loopback Paths” filed Dec. 18, 2018, both ofwhich are hereby incorporated by reference as if reproduced in theirentirety.

BACKGROUND 1. Field

The field relates to testing of integrated circuit packages.

2. Description of the Related Art

After an integrated circuit has been installed in its package or module,the integrated circuit needs to be tested for functionality. This isdone using a device called a tester, which makes contact with theintegrated circuit package and provides appropriate electrical signalsto test the functionality of the integrated circuit. Conventionally,integrated circuit packages or modules have pins or balls on the bottomor sides which are contacted by the tester and test signals are providedthrough the pins or balls. Recent advances have changed the packaging ofradio frequency (RF) integrated circuits so that rather thantransmitting the RF signals through the balls or pins to an antennamodule, antennas are provided on the top surface of package itself. Thisis called an AOP or antenna on package configuration. When the RFsignals were provided through the pins or balls, it was simple to testthe RF circuitry using conventional means on the tester. But because theantennas are not connected to the pins or balls and are provided only onthe package in an AOP design, conventional testing methods do not workfor testing of the outputs of and inputs to the RF circuits. This hascomplicated testing of such packages.

SUMMARY

An RF loopback substrate or printed circuit board (PCB) contains receiveand transmit antennas located on the bottom of the loopback substratewhich are aligned with the complementary transmit and receive antennason an AOP device under test. The loopback substrate receive and transmitantennas are coupled to each other through a combining and dividingnetwork so that signals received at any receive antenna can be providedto any transmit antennas. The package contacts are driven by aconventional tester, which in turn causes RF circuitry in the integratedcircuit to drive an AOP transmit antenna. The corresponding loopbacksubstrate receive antenna receives the RF signal from the AOP transmitantenna and provides it to the loopback substrate transmit antennas. Theintegrated circuit package AOP receive antennas then receive the RFsignals from the loopback substrate transmit antennas. The signals atthe integrated circuit package AOP receive antennas are monitoredthrough the integrated circuit contacts as is normal to monitor thereceived RF signals. This allows testing of both the RF circuitry andthe AOP antennas using a conventional tester. The loopback substrate ismounted into an integrated circuit package handler used with the testerto allow the testing to be done automatically in normal fashion.

BRIEF DESCRIPTION OF THE FIGURES

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1 is a diagram of an integrated circuit tester.

FIG. 2 is a diagram of an integrated circuit package including antennason the package.

FIG. 3 is a diagram of the integrated circuit package of FIG. 2 withtesting relationships illustrated.

FIG. 4 is a diagram of the integrated circuit package of FIG. 2 inconjunction with an antenna on package loopback substrate or printedcircuit board.

FIG. 4A is a diagram of an interconnect network between the receiveantennas and the transmit antennas on a loopback substrate.

FIG. 4B is a diagram of a Wilkinson divider.

FIG. 4C is a diagram of printed circuit board traces forming theWilkinson divider of FIG. 4B.

FIG. 5 is a diagram of the antenna on package loopback substrate of FIG.4 installed in the handler with an integrated circuit package to betested.

FIG. 6 is a flowchart of test operations using the antenna on packageloopback substrate of FIG. 4.

FIG. 7A is a diagram of one version of a handler for holding the antennaon package loopback substrate of FIG. 4.

FIG. 7B is a diagram of a second version of a handler for holding theantenna on package loopback substrate of FIG. 4.

DETAILED DESCRIPTION

Referring now to FIG. 1, an integrated circuit tester 100 isillustrated. A tester body 102 contains the various computing elementsand signal analysis elements of the tester 100. A test board 104 whichinterfaces between the tester body 102 and a contactor 106 is installedon the tester body 102. Contactor 106 provides an interface between thetest board 104 and the actual device under test 108. In operation of thetester 100, the device under test 108 is held by a handler 110, with thedevice under test 108 being held in place in one version by the use of avacuum provided through a vacuum line 112 connected to ports 113 andinternal lines 115. It is understood that the use of vacuum to hold thedevice under test in the handler is exemplary and other techniques arewell known.

An automated handler 110 is connected to a manipulator arm 114, which isin turn connected to a manipulator gantry 116. The manipulator arm 114and the manipulator gantry 116 are controlled such that the handler 110is movable between a position to pick up a new device to be tested andthen move the device to the tester body 102 so that the device undertest 108 is connected to the contactor 106 and a test is performed. Whenthe test is completed, the handler 110 is moved by the manipulator arm114 and the manipulator gantry 116 to allow the device under test 108 tobe deposited in good or bad tested circuit locations. It is understoodthat this is a very simplified illustration of a tester for purposes ofexplanation and it is understood that there are many different testerconfigurations with many distant different handler assemblies andmanipulator and gantry assemblies.

FIG. 2 illustrates an AOP device 200 which is to be tested. The AOPdevice 200 includes a package or module 202, which contains theintegrated circuit. Electrical connections to the contained integratedcircuit are made through a series of contacts or balls 204 in theillustrated AOP device 200. It is understood that pins could be utilizedinstead of balls 204 as is common. Located on the top or upper surface206 of the package 202 are transmit antennas 208A, 208B and 208C.Receive antennas 210A, 210B, 210C and 210D are also located on the topor upper surface 206 of the package 202. The receive antennas 210A-210Dand the transmit antennas 208A-208C are the antennas in the antenna onpackage design. The transmit antennas 208A-208C are connected internallyin the package 202 to RF drivers of the integrated circuit. The receiveantennas 210A-210D are connected internally in the package 202 to RFreceive buffers of the integrated circuit.

FIG. 3 illustrates one variation of signal testing that is to beperformed. The arrows in FIG. 3 illustrate that each of the transmitantennas 208A208C is tested against each of the receive antennas202A-210D.

FIG. 4 illustrates an RF loopback substrate or PCB 400 in relation tothe AOP device 200 to be tested. The RF loopback substrate 400 includesa PCB 401 configured to complement the AOP device 200. Receive antennas402A, 402B and 402C are located on the bottom surface 403 of the PCB 401and in locations that are complementary to the transmit antennas 208A,208B and 208C to form receive-transmit pairs when in operation.Similarly, transmit antennas 404A, 404B, 404C and 404D are present onthe bottom surface 403 of the PCB 401 in locations complementary to thereceive antennas 210A, 210B, 210C and 210D to form transmit-receivepairs when in operation. The receive antennas 402A-402C are connected tothe transmit antennas 404A-404D using an interconnect 406, explained inmore detail in FIGS. 4A-4C. The size and shape of the loopback substrate400 are such that the receive antennas 402A, 402B and 402C and transmitantennas 404A, 404B, 404C and 404D are complementary to the respectivetransmit antennas 208A, 208B and 208C and receive antennas 210A, 210B,210C and 210D and are touching or separated by a small gap. The gap maybe an air gap.

In operation, the RF loopback substrate 400 is located over and incontact or close to the AOP device 200 under test. Signals are providedto the AOP device 200 through the balls 204 to cause RF signals to betransmitted by each of the RF transmit antennas 208A-208C. The signalsprovided from a transmit antenna 208A-208C are then received by thecomplementary receive antenna 402A-402C. The signals are then providedfrom the receive antenna 402A-402C to the transmit antennas 404A-404D.An RF signal is then provided from the transmit antennas 404A-404D tothe receive antennas 210A-210D. The signals received at the receiveantennas 210A-210D are then monitored to determine if the RF transmitand RF receive circuitry in the AOP device 200 is functional.

FIGS. 4A-4C provide details on the interconnect 406. In one design thereceive antennas 402A, 402B and 402C and the transmit antennas 404A,404B, 404C and 404D are provided on a first or face down layer of thePCB that is the loopback substrate 400. A feed trace 406A, 406B and 406Cis provided in a next layer from respective receive antennas 402A, 402Band 402C, while feed traces 408A, 408B, 408C and 408D are provided inthat same layer from respective transmit antennas 404A, 404B, 404C and404D. A ground layer forms the next layer this design. Vias (not shown)are provided from the feed traces 406A, 406B and 406C to receivemicrostrip lines 410A, 410B and 410C on a final or top layer.Microstrips are used in this design as the design is a radar integratedcircuit. Microstrips 412A, 412B, 412C and 412D are connected to the feedtraces 408A, 408B, 408C and 408D on the top layer. Microstrip lines 410Aand 410B are connected to a Wilkinson divider 414A. Microstrip lines410C and 422 are connected to a Wilkinson divider 414B. A terminatingresistor 424 is connected to microstrip line 422.

A Wilkinson divider is a passive power divider circuit that achievesisolation between the output ports while maintaining a matched conditionon all ports. The Wilkinson divider design can also be used as a powercombiner because it is made up of passive components and hencereciprocal. Referring to FIGS. 4B and 4C, a Wilkinson divider 480 isshown in more detail. A port P1 482 is the input port if operating as adivider and the output port if operating as a combiner. Ports P2 484 andP3 486 are the output ports if operating as a divider and the inputports if operating as a combiner. A resistor 488 is connected betweenports P2 484 and P3 486 as part of the Wilkinson divider configuration.As shown in FIG. 4C, in the one design, the microstrips at each porthave a 50Ω impedance. The loop of the Wilkinson divider 480 has a 70.7Ωimpedance.

As a power divider, when a signal enters port P1 482, the signal splitsinto equal-amplitude, equal-phase output signals at ports P2 484 and P3486. Since each end of the resistor 488 between ports P2 484 and P3 486is at the same potential, no current flows through it and therefore theresistor 488 is decoupled from the input. As a power combiner, a signalis input at port P2 484. In this case, the signal splits equally betweenport P1 482 and the resistor 488 with none appearing at port P3 486. Theresistor 488 thus serves the function of decoupling ports P2 484 and P3486. Note that for a signal input at either port P2 484 or P3 486, halfthe power is dissipated in the resistor 488 and half is delivered toport P1 482.

Wilkinson dividers 414A and 414B are configured as power combiners. InFIG. 4A, a signal with power a² is provided from receive antenna 402B toWilkinson divider 414A. A signal with power

$\frac{a^{2}}{2}$

is provided from the Wilkinson divider 414A to a Wilkinson divider 416acting as a combiner for the outputs of Wilkinson divider 414A andWilkinson divider 414B. A signal with power

$\frac{a^{2}}{4}$

is provided from the Wilkinson divider 416 to a Wilkinson divider 418acting as a divider. A signal with power

$\frac{a^{2}}{8}$

is provided from the outputs of the Wilkinson divider 418 to the inputsof Wilkinson dividers 420A and 420B. The outputs of Wilkinson divider420A have a signal with a power of

$\frac{a^{2}}{16}$

and are connected to microstrips 412A and 412B, so that transmitantennas 404A, 404B each receive a signal with a power of

$\frac{a^{2}}{16}.$

The outputs of Wilkinson divider 420B have a signal with a power of

$\frac{a^{2}}{16}$

and are connected to microstrips 412C and 412D, so that transmit antenna404C, 404D receive a signal with a power of

$\frac{a^{2}}{16}$

and a resistor 424 connected to microstrip 422 receives a signal with apower of

$\frac{a^{2}}{16}.$

Thus, driving any one of the transmit antennas 208A-208C results in anequal signal at each of the receive antennas 201A-210D when everythingis operating correctly. In one design the insertion loss from thereceive antenna 402A-402C to the transmit antennas 404A-404D is 15 to 17db, which is 3 db per Wilkinson divider and 3 to 5 db for trace loss.

If the AOP device 200 has only one transmit antenna and one receiveantenna, the Wilkinson dividers are not necessary and the receiveantenna and the transmit antenna on the loopback substrate 400 can bedirectly connected by a microstrip.

While Wilkinson dividers are appropriate for the radar frequencies ofthe one design, in other designs other passive RF dividers, combiners,splitters, hybrids and couplers can be used as appropriate for therelevant signal frequency. Active components can be utilized as well,though provisions must be made to provide power while in the handler.

FIG. 5 illustrates the relationship of the AOP device 200 and the RFloopback substrate 400 when the RF loopback substrate 400 is installedin the handler 110 and the AOP device 200 is near location in thehandler 110. This shows a good view of the proximity of the transmitantennas 208A-208C and the receive antennas 402A-402C. Similarly, therelationship between the transmit antenna 404D and the receive antenna210D is illustrated. The distance or gap between the antennas ispreferably a nominal amount, such as between zero and 0.2 mm. Directcontact or zero distance is possible as a thin layer of solder-resistcovers the antennas on the AOP device 200. The internal lines 115 havebeen modified to internal lines 500 in the illustration of FIG. 5 toclear the loopback substrate 400 and yet properly cooperate with thedevice under test.

FIG. 6 is a flowchart of operations to perform the tests as illustratedin FIG. 3. In step 600 the device under test (DUT), the AOP device 200,is captured by the handler 110, so that the DUT is adjacent the loopbacksubstrate 400. In step 602, the handler 110 is moved to place the AOPdevice 200 in contact with the tester 100, that is, in contact with thecontactor 106. With the AOP device 200 now properly in place, initialdevice testing is performed in step 604. To commence RF and circuitrytesting in step 606, a TX value is set to one, for TX1-TX3 in the designof FIGS. 2-4. In step 608, the first transmit antenna 208A is driven andthe signal at each receive antenna 210A-210D is measured. The receivedsignal is converted to receive gain to determine if the transmit toreceive path is functioning within specification. After measurements andcalculations are completed, in step 610 the TX value is incremented. Instep 612 it is determined if the last of the transmit antennas has beentested. If not, operation returns to step 608 and the next transmitantenna 208B-208C is tested. If this was the last transmit antenna, suchas transmit antenna 208C, in step 614 any final device tests areperformed. In step 620 the handler 110 moves the AOP device 200 undertest to the proper location based on a pass/fail determination of thevarious testing. While driving only a single transmit antenna 208A-208Chas been described, driving of combinations of the transmit antennas208A-208C is also available for more complete testing.

FIGS. 7A and 7B illustrate alternative handler 110 configurations forholding the RF loopback substrate 400. In FIG. 7A, a handler body 702has a bottom surface 703 that contains a groove 704 sized to hold an RFloopback substrate 706. A chamber 707 inside the handler body 702 andabove the RF loopback substrate 706 is an empty volume. An opening 708is present in the handler body 702 to allow mating with the AOP device200 under test to align the AOP device 200 and the RF loopback substrate706. In FIG. 7B, an alternative handler body 712 as illustrated. The RFloopback substrate 706 is located in the chamber 707 and a shim 714 ispresent to fill up the volume of the chamber 707. The bottom or lowerportion 716 of the chamber 707 includes a lip 718 to retain the RFloopback substrate 706 in the chamber 707.

It is understood that other handler body designs to hold the RF loopbacksubstrate in proper alignment with the AOP device under test can easilybe developed based on the specifics of the individual tester.

While this description has focused on antenna on package devices, theloopback substrate will also work with antenna in package (AIP) devicesand other designs where the RF signals are provided directly from orreceived directly at the device without going through device balls orpins.

By the use of a loopback substrate containing interconnected receive andtransmit antennas that are complementary to the transmit and receiveantennas of an AOP package under test, testing of the RF circuitry andantennas of the AOP package can be performed as part of the normal testsequence, without any special handling or steps.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples may be used incombination with each other. Many other examples will be upon reviewingthe above description. The scope should, therefore, be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled. In the appended claims,the terms “including” and “in which” are used as the plain-Englishequivalents of the respective terms “comprising” and “wherein.”

What is claimed is:
 1. An apparatus for use with an integrated circuitpackage having a transmit antenna and a receive antenna on a top surfaceof the integrated circuit package, the apparatus comprising: a handlerbody including: a bottom surface for mating with the integrated circuitpackage; a port for receiving a vacuum line; and at least one line totransfer vacuum from the port to the bottom surface; a loopbacksubstrate including: a bottom surface; a transmit antenna located on thebottom surface of the loopback substrate; and a receive antenna coupledto the loopback substrate transmit antenna and located on the bottomsurface of the loopback substrate, wherein a location of the loopbacksubstrate receive antenna is complementary to a location of theintegrated circuit package transmit antenna to form a receive-transmitpair when operating and a location of the loopback substrate transmitantenna is complementary to a location of the integrated circuit packagereceive antenna to form a transmit-receive pair when operating, andwherein the handler body is adapted to hold the loopback substrate in alocation above the bottom surface of the handler body so that a nominalgap results when the integrated circuit package is mated with thehandler body.
 2. The apparatus of claim 1, wherein the nominal gap iszero to 0.2 mm.
 3. The apparatus of claim 1, wherein the handler bodyfurther includes: a groove to hold the loopback substrate; and a chamberabove the loopback substrate.
 4. The apparatus of claim 1, wherein thehandler body further includes: a chamber above the bottom surface of thehandler body, the chamber having a lip at a lower portion to retain theloopback substrate; and a shim located above the loopback substrate tosubstantially fill the volume of the chamber.
 5. The apparatus of claim1, wherein the loopback substrate further includes components on theloopback substrate to couple the loopback substrate receive antenna tothe loopback substrate transmit antenna, wherein the components arepassive components.
 6. The apparatus of claim 1, wherein the integratedcircuit package has a plurality of integrated circuit package transmitantennas or a plurality of integrated circuit package receive antennas,the plurality of integrated circuit package transmit antennas includingthe integrated circuit package transmit antenna or the plurality ofintegrated circuit package receive antennas including the integratedcircuit package receive antenna, and wherein the loopback substratefurther includes: a plurality of loopback substrate receive antennascoupled to the loopback substrate transmit antenna or a plurality ofloopback substrate transmit antennas coupled to the loopback substratereceive antenna, the plurality of loopback substrate receive antennasincluding the loopback substrate receive antenna or the plurality ofloopback substrate transmit antennas including the loopback substratetransmit antenna, wherein, for each of the plurality of loopbacksubstrate receive antennas, a location of a given loopback substratereceive antenna in the plurality of loopback substrate receive antennasis complementary to a location of a respective integrated circuitpackage transmit antenna in the plurality of integrated circuit packagetransmit antennas to form receive-transmit pairs when operating, or foreach of the plurality of loopback substrate transmit antennas, alocation of a given loopback substrate transmit antenna in the pluralityof loopback substrate transmit antennas is complementary to a locationof a respective integrated circuit package receive antenna in theplurality of integrated circuit package receive antennas to formtransmit-receive pairs when operating, and components including at leastone of a radio frequency (RF) divider, RF combiner, RF splitter, RFhybrid and RF coupler to couple the plurality of loopback substratereceive antennas to the loopback substrate transmit antenna or theplurality of loopback substrate receive antennas to the loopbacksubstrate transmit antenna.
 7. The apparatus of claim 6, wherein thecomponents include at least one Wilkinson divider and a plurality ofmicrostrips to couple the Wilkinson divider to the plurality of loopbacksubstrate receive antennas or the plurality of loopback substratetransmit antennas.
 8. The apparatus of claim 6, wherein the integratedcircuit package has a plurality of integrated circuit package transmitantennas and a plurality of integrated circuit package receive antennas,the plurality of integrated circuit package transmit antennas includingthe integrated circuit package transmit antenna and the plurality ofintegrated circuit package receive antennas including the integratedcircuit package receive antenna, and wherein the loopback substrateincludes: a plurality of loopback substrate receive antennas and aplurality of loopback substrate transmit antennas coupled to theplurality of loopback substrate receive antennas, the plurality ofloopback substrate receive antennas including the loopback substratereceive antenna and the plurality of loopback substrate transmitantennas including the loopback substrate transmit antenna, wherein, foreach of the plurality of loopback substrate receive antennas, a locationof a given loopback substrate receive antenna in the plurality ofloopback substrate receive antennas is complementary to a location of arespective integrated circuit package transmit antenna in the pluralityof integrated circuit package transmit antennas to form receive-transmitpairs when operating, and for each of the plurality of loopbacksubstrate transmit antennas, a location of a given loopback substratetransmit antenna in the plurality of loopback substrate transmitantennas is complementary to a location of a respective integratedcircuit package receive antenna in the plurality of integrated circuitpackage receive antennas to form transmit-receive pairs when operating,and components including a plurality of Wilkinson dividers and aplurality of microstrips to couple the plurality of Wilkinson dividersto the plurality of loopback substrate receive antennas and theplurality of loopback substrate transmit antennas.
 9. The apparatus ofclaim 6, wherein the integrated circuit package has a plurality ofintegrated circuit package transmit antennas and a plurality ofintegrated circuit package receive antennas, the plurality of integratedcircuit package transmit antennas including the integrated circuitpackage transmit antenna and the plurality of integrated circuit packagereceive antennas including the integrated circuit package receiveantenna, and wherein the loopback substrate further includes: aplurality of loopback substrate receive antennas and a plurality ofloopback substrate transmit antennas coupled to the plurality ofloopback substrate receive antennas, the plurality of loopback substratereceive antennas including the loopback substrate receive antenna andthe plurality of loopback substrate transmit antennas including theloopback substrate transmit antenna, wherein, for each of the pluralityof loopback substrate receive antennas, a location of a given loopbacksubstrate receive antenna in the plurality of loopback substrate receiveantennas is complementary to a location of a respective integratedcircuit package transmit antenna in the plurality of integrated circuitpackage transmit antennas to form receive-transmit pairs when operating,and for each of the plurality of loopback substrate transmit antennas, alocation of a given loopback substrate transmit antenna in the pluralityof loopback substrate transmit antennas is complementary to a locationof a respective integrated circuit package receive antenna in theplurality of integrated circuit package receive antennas to formtransmit-receive pairs when operating, and components including aplurality of any of RF dividers, RF combiners, RF splitters, RF hybridsand RF couplers and a plurality of microstrips to couple the pluralityof any of RF dividers, RF combiners, RF splitters, RF hybrids and RFcouplers to the plurality of loopback substrate receive antennas and theplurality of loopback substrate transmit antennas.
 10. A loopbacksubstrate for use with an integrated circuit package having a transmitantenna and a receive antenna located on a top surface of the integratedcircuit package, the loopback substrate including: a bottom surface; atransmit antenna located on the bottom surface of the loopbacksubstrate; and a receive antenna located on the bottom surface of theloopback substrate and coupled to the loopback substrate transmitantenna, wherein a location of the loopback substrate receive antenna iscomplementary to a location of the integrated circuit package transmitantenna to form a receive-transmit pair when operating and a location ofthe loopback substrate transmit antennas is complementary to a locationof the integrated circuit package receive antenna to form atransmit-receive pair when operating.
 11. The loopback substrate ofclaim 10, further comprising: components on the loopback substrate tocouple the loopback substrate receive antenna to the loopback substratetransmit antenna, wherein the components are passive components.
 12. Theloopback substrate of claim 10, wherein the integrated circuit packagehas a plurality of integrated circuit package transmit antennas or aplurality of integrated circuit package receive antennas, the pluralityof integrated circuit package transmit antennas including the integratedcircuit package transmit antenna or the plurality of integrated circuitpackage receive antennas including the integrated circuit packagereceive antenna, and wherein the loopback substrate further comprises: aplurality of loopback substrate receive antennas coupled to the loopbacksubstrate transmit antenna or a plurality of loopback substrate transmitantennas coupled to the loopback substrate receive antenna, theplurality of loopback substrate receive antennas including the loopbacksubstrate receive antenna or the plurality of loopback substratetransmit antennas including the loopback substrate transmit antenna,wherein, for each of the plurality of loopback substrate receiveantennas, a location of a given loopback substrate receive antenna inthe plurality of loopback substrate receive antennas is complementary toa location of a respective integrated circuit package transmit antennain the plurality of integrated circuit package transmit antennas to formreceive-transmit pairs when operating, or for each of the plurality ofloopback substrate transmit antennas, a location of a given loopbacksubstrate transmit antenna in the plurality of loopback substratetransmit antennas is complementary to a location of a respectiveintegrated circuit package receive antenna in the plurality ofintegrated circuit package receive antennas to form transmit-receivepairs when operating, and components including at least one of a radiofrequency (RF) divider, RF combiner, RF splitter, RF hybrid and RFcoupler to couple the plurality of loopback substrate receive antennasto the loopback substrate transmit antenna or the plurality of loopbacksubstrate receive antennas to the loopback substrate transmit antenna.13. The loopback substrate of claim 12, wherein the components includeat least one Wilkinson divider and a plurality of microstrips to couplethe Wilkinson divider to the plurality of loopback substrate receiveantennas or the loopback substrate plurality of transmit antennas. 14.The loopback substrate of claim 12, wherein the integrated circuitpackage has a plurality of transmit antennas and a plurality of receiveantennas, the plurality of integrated circuit package transmit antennasincluding the integrated circuit package transmit antenna and theplurality of integrated circuit package receive antennas including theintegrated circuit package receive antenna, and wherein the loopbacksubstrate further comprises: a plurality of loopback substrate receiveantennas and a plurality of loopback substrate transmit antennas coupledto the plurality of loopback substrate receive antennas, the pluralityof loopback substrate receive antennas including the loopback substratereceive antenna and the plurality of loopback substrate transmitantennas including the loopback substrate transmit antenna, wherein, foreach of the plurality of loopback substrate receive antennas, a locationof a given loopback substrate receive antenna in the plurality ofloopback substrate receive antennas is complementary to a location of arespective integrated circuit package transmit antenna in the pluralityof integrated circuit package transmit antennas to form receive-transmitpairs when operating, and for each of the plurality of loopbacksubstrate transmit antennas, a location of a given loopback substratetransmit antenna in the plurality of loopback substrate transmitantennas is complementary to a location of a respective integratedcircuit package receive antenna in the plurality of integrated circuitpackage receive antennas to form transmit-receive pairs when operating,and components including a plurality of Wilkinson dividers and aplurality of microstrips to couple the plurality of Wilkinson dividersto the plurality of loopback substrate receive antennas and theplurality of loopback substrate transmit antennas.
 15. The loopbacksubstrate of claim 12, wherein the integrated circuit package has aplurality of integrated circuit package transmit antennas and aplurality of integrated circuit package receive antennas, the pluralityof integrated circuit package transmit antennas including the integratedcircuit package transmit antenna and the plurality of integrated circuitpackage receive antennas including the integrated circuit packagereceive antenna, and wherein the loopback substrate further comprises: aplurality of loopback substrate receive antennas and a plurality ofloopback substrate transmit antennas coupled to the plurality ofloopback substrate receive antennas, the plurality of loopback substratereceive antennas including the loopback substrate receive antenna andthe plurality of loopback substrate transmit antennas including theloopback substrate transmit antenna, wherein, for each of the pluralityof loopback substrate receive antennas, a location of a given loopbacksubstrate receive antenna in the plurality of loopback substrate receiveantennas is complementary to a location of a respective integratedcircuit package transmit antenna in the plurality of integrated circuitpackage transmit antennas to form receive-transmit pairs when operating,and for each of the plurality of loopback substrate transmit antennas, alocation of a given loopback substrate transmit antenna in the pluralityof loopback substrate transmit antennas is complementary to a locationof a respective integrated circuit package receive antenna in theplurality of integrated circuit package receive antennas to formtransmit-receive pairs when operating, and components including aplurality of any of RF dividers, RF combiners, RF splitters, RF hybridsand RF couplers and a plurality of microstrips to couple the pluralityof any of RF dividers, RF combiners, RF splitters, RF hybrids and RFcouplers to the plurality of loopback substrate receive antennas and theplurality of loopback substrate transmit antennas.
 16. A method oftesting an integrated circuit package having a transmit antenna and areceive antenna located on a top surface of the integrated circuitpackage and a plurality of electrical contacts located on a bottomsurface of the integrated circuit package, the method comprising:locating a loopback substrate adjacent the top surface of the integratedcircuit package, the loopback substrate including: a bottom surface; atransmit antenna located on the bottom surface of the loopbacksubstrate; and a receive antenna coupled to the loopback substratetransmit antenna and located on the bottom surface of the loopbacksubstrate, wherein a location of the loopback substrate receive antennais complementary to a location of the integrated circuit packagetransmit antenna to form a receive-transmit pair when operating and alocation of the loopback substrate transmit antenna is complementary toa location of the integrated circuit package receive antenna to form atransmit-receive pair when operating; providing electrical signals tothe plurality of electrical contacts of the integrated circuit packageto cause signals to be driven by the integrated circuit package transmitantenna on the integrated circuit package to the loopback substratereceive antenna and to be received by the integrated circuit packagereceive antenna on the integrated circuit package from the loopbacksubstrate transmit antenna; and monitoring the plurality of electricalcontacts of the integrated circuit package to evaluate the signalsreceived at the integrated circuit package receive antenna when theintegrated circuit package transmit antenna is being driven.
 17. Themethod of claim 16, wherein the adjacent location of the bottom surfaceof the loopback substrate is a nominal distance from the top surface ofthe integrated circuit package.
 18. The method of claim 17, wherein thenominal distance is zero to 0.2 mm.
 19. The method of claim 16, whereinthe integrated circuit package has a plurality of integrated circuitpackage transmit antennas or a plurality of integrated circuit packagereceive antennas, the plurality of integrated circuit package transmitantennas including the integrated circuit package transmit antenna orthe plurality of integrated circuit package receive antennas includingthe integrated circuit package receive antenna, and wherein the loopbacksubstrate further includes: a plurality of loopback substrate receiveantennas coupled to the loopback substrate transmit antenna or aplurality of loopback substrate transmit antennas coupled to theloopback substrate receive antenna, the plurality of loopback substratereceive antennas including the loopback substrate receive antenna or theplurality of loopback substrate transmit antennas including the loopbacksubstrate transmit antenna, wherein, for each of the plurality ofloopback substrate receive antennas, a location of a given loopbacksubstrate receive antenna in the plurality of loopback substrate receiveantennas is complementary to a location of a respective integratedcircuit package transmit antenna in the plurality of integrated circuitpackage transmit antennas to form receive-transmit pairs when operating,or for each of the plurality of loopback substrate transmit antennas, alocation of a given loopback substrate transmit antenna in the pluralityof loopback substrate transmit antennas is complementary to a locationof a respective integrated circuit package receive antenna in theplurality of integrated circuit package receive antennas to formtransmit-receive pairs when operating, and components including at leastone Wilkinson divider and a plurality of microstrips to couple theWilkinson divider to the plurality of loopback substrate receiveantennas or the plurality of loopback substrate transmit antennas. 20.The method of claim 16, wherein the integrated circuit package has aplurality of integrated circuit package transmit antennas and aplurality of integrated circuit package receive antennas, the pluralityof integrated circuit package transmit antennas including the integratedcircuit package transmit antenna and the plurality of integrated circuitpackage receive antennas including the integrated circuit packagereceive antenna, and wherein the loopback substrate further includes: aplurality of loopback substrate receive antennas and a plurality ofloopback substrate transmit antennas coupled to the plurality ofloopback substrate receive antennas, the plurality of loopback substratereceive antennas including the loopback substrate receive antenna andthe plurality of loopback substrate transmit antennas including theloopback substrate transmit antenna, wherein, for each of the pluralityof loopback substrate receive antennas, a location of a given loopbacksubstrate receive antenna in the plurality of loopback substrate receiveantennas is complementary to a location of a respective integratedcircuit package transmit antenna in the plurality of integrated circuitpackage transmit antennas to form receive-transmit pairs when operating,and for each of the plurality of loopback substrate transmit antennas, alocation of a given loopback substrate transmit antenna in the pluralityof loopback substrate transmit antennas is complementary to a locationof a respective integrated circuit package receive antenna in theplurality of integrated circuit package receive antennas to formtransmit-receive pairs when operating, and components including aplurality of Wilkinson dividers and a plurality of microstrips to couplethe plurality of Wilkinson dividers to the plurality of loopbacksubstrate receive antennas and the plurality of loopback substratetransmit antennas.